Taxol, a compound exhibiting an antitumor activity on the basis of an inhibitory action against depolymerization of microtubules during cell division, is expected to be effective in clinical application as an antitumor agent having a mode of action different from that of conventional antitumor agents. Various kinds of taxol derivatives have so far been disclosed in publications. For example, compounds are disclosed in which a substituent is introduced on the pyridine ring of the side chain at the 13-position to suppress the modification of the compounds by metabolism (International Publication WO 01/27115). In particular, the compound described in Example 7 of the aforementioned international publication [(1S,2S,3R,4S,5R,8R, 9S,10R,13S)-4-acetoxy-2-benzoyloxy-9,10-[(1S)-2-(dimethylamino)ethylidenedioxy]-5,2 0-epoxy-1-hydroxytax-11-en-13-yl (2R,3S)-3-(tert-butoxycarbonylamino)-3-(3-fluoro-2-pyridyl)-2-hydroxypropionate] is hardly metabolized by human liver microsomes and expected as an antitumor agent that can be orally administered.
As for the compound described in Example 7 of the aforementioned international publication, the method for preparation of the compound is also described in Example 9 of the publication, as well as in Example 7. Example 9 describes that the target compound was obtained by “performing an operation similar to that of Step 4 of Example 8”. According to that explanation, it is considered that the solvent in the extract of the reaction mixture containing the target compound was evaporated, and the residue was purified by using silica gel chromatography and recrystallized from a mixture of water and ethanol to obtain a solid deduced to be crystals of the target compound. However, no physicochemical value is given in Examples 7 and 9 of the aforementioned international publication that evidences the isolation of the aforementioned compound in the form of a crystal.